using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int level = 0;
            List<String> list = new List<string>();
            List<String> items = new List<string>();
            for (int i = 0; i < N; i++)
            {
                list.AddRange(Console.ReadLine().Split(' '));
            }
            foreach (String con in list)
            {
                if (!items.Contains(con))
                {
                    items.Add(con);
                }
                else
                {
                    items.Remove(con);
                    level++;
                }
            }
            level = level + items.Count / 4;
            Console.WriteLine(level);
        }
    }
}